My workshop is an old one-room schoolhouse built in 1931, 24' X 32' with 12' ceiling. Some ceiling insulation but nothing in the walls and the building is not particularly air tight. The original a/c unit in the building when I acquired it in 1990 has finally failed; the building is in full sun and by mid afternoon gets far too hot inside to do any kind of work without a/c.

The original unit is a 23,000 BTU window a/c mounted in a hole in the wall. Plugging numbers into various on-line calculators for the size of the space and the fact that some of the equipment in the shop gives off considerable heat when operating, I get recommendations all the way from 12k to nearly 30k. The closest thing I can find locally to the original is 25k. However, I suspect the old unit was working at nowhere its rated rated specs, long before it finally quit.

Here are some questions I have before deciding on a replacement:

1. It is said that overkill with too large a unit won't dehumidify well, leaving the room feeling cold and clammy. But wouldn't installing a somewhat over-size unit but keeping it on medium or low settings, allow it to run it less hard, more quietly and maybe last longer? Is running a larger unit on medium or low settings not equivalent to running a smaller unit on high?

2. The hole in the wall is 8' off the floor. I'm interested in any suggestions for safely removing the old one and installing the new one. Any lift or scaffolding has to be small and lightweight enough to go up a few steps and then through a 34" door, and there is limited open space inside the building. A scissor lift would be out of the question.

If I built a platform 4' high I believe two people could lift the unit to the platform, and then stand on the platform and lift it another 4' to the final destination. The outer case of the new unit would already be installed in place, ready to accept the inner workings. But I would be interested in any other suggestions. Replacement units that I have checked out all weigh between around 100 to 150 lbs.

3. This is primarily an electronics workshop with some highly sensitive equipment inside. Despite their claimed higher efficiency and lower operating costs, I am concerned about radio-frequency interference from the variable speed motors and switching DC power supplies in some of the newer higher-tech a/c units, so I am inclined to stay with traditional on/off thermostatic control. Has anyone had any specific experiences with this?

4. The brand names most widely available in local stores are LG, General Electric and Frigidaire. Checking on-line reviews and talking with some local users, I am leaning towards Frigidaire, which seems to get the best overall reviews. G-E gets a lot of negative comments concerning reliability, poor technical support and difficulty finding replacement parts. My greatest concern with LG is the likelihood of RF interference as described above, plus the ultimate long term reliability of their cutting-edge technology.

Any helpful comments would be appreciated.

Don